Drum and drum-set tuner

ABSTRACT

A resonance tuner receives and digitizes an analog signal in response to a resonance of a structure thereby creating a plurality of time samples. A series of the time samples are buffered upon burst detection. A power spectrum is estimated by computing a Time-To-Frequency-Transform of the series of time samples and a magnitude of each of the resulting frequency samples is squared. At least one subset associated with at least one spectral peak is selected from the frequency samples. Each spectral peak has at least one sample with a sufficient magnitude and being spectrally adjacent to any other sample in another spectral peak by less than a threshold. A fundamental spectral peak is determined in a fundamental subset including a spectral peak with a sample at the lowest frequency greater than zero. The fundamental spectral peak has the sample with the largest magnitude within the fundamental subset.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation patent application of allowed U.S.patent application Ser. No. 14/101,845 filed Dec. 10, 2013, entitled,“DRUM AND DRUM-SET TUNER”, which is a continuation patent application ofallowed U.S. patent application Ser. No. 13/004,166, filed on Jan. 11,2011, now issued as U.S. Pat. No. 8,642,874 entitled, “DRUM AND DRUM-SETTUNER”, which claims priority to expired U.S. Provisional ApplicationNo. 61/297,578 filed on Jan. 22, 2010 entitled “DRUM AND DRUM-SETTUNER,” the entireties of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates generally to spectral analysis. More specifically,the invention relates to detection of a fundamental frequency tofacilitate tuning of a resonant structure.

BACKGROUND

A variety of structures resonate with a fundamental frequency oftencombined with a plurality of other frequencies that make detection andanalysis of the fundamental frequency problematic. Furthermore, manystructures resonant for only a short period of time. A particularexample of a resonant structure is a drum.

In one example, a drum consists of a hollow cylinder with a circularmembrane clamped to either or both ends of the cylinder. A circularmembrane that is suspended under tension at its outer perimeter iscapable of several modes of vibration including circular symmetric andangular modes. The circular modes are described by a series offirst-order Bessel functions for example and are therefore notharmonically related. The frequency of vibration depends, in part, onthe radius, tension and density of the membrane. A cylindrical aircolumn also resonates with the frequency of resonance depending on thelength of the drum and the speed of sound and whether or not the ends ofthe cylinder are open or closed. Furthermore, the combination of acylindrical shell and cylindrical membranes resonates as a system at avariety of frequencies that depend on a number of parameters, such asthe dimensions of the drum, the tension and density of the drum-headsand the composition of the shell.

In one example, a drum-head is held by a metal or wooden hoop that isattached to a drum shell with several adjustable tension screws. Thetension of the drum-head is determined by the force exerted by thetension screws. Tuning involves adjusting the tension screws to achievea uniform pitch over a drum-head. When the pitch is uniform around theperimeter of the drum, the drum-head is considered to be “cleared” or“in tune with itself.” In addition to being in tune with itself, eachdrum-head needs to be adjusted to a pitch that produces the desiredoverall sound. It is sometimes desirable to tune each head separatelywith the other held damped to prevent vibration.

Striking a drum produces a percussive sound that's shorter in durationthan any non-percussive musical instrument. The time-domain response ofa typical drum, consists of an oscillatory signal with an abrupt onsetfollowed by a short, approximately exponential, decay. Air pressureacting on the large area of the drum-head limits the duration of thesound. A vibrating string on the other hand has a much smaller area thana drum-head and vibrates much longer in comparison.

Tuning a set of drums poses additional challenges for musician. Somedrummers tune their drums to a musical chord such as a major chord.Other drummers tune their drums to relative tonic intervals such asthirds or fifths, and still others tune by ear to something suitingtheir musical taste. The choice of specific drum pitches sometimesdepends on the type of music being played. A drum-set might be tunedhigher for jazz than for rock, for example, or it might be tuned open toresonate for a live performance or tight for a recording. Tuning alsodepends on the size and type of drum. A larger diameter drum is usuallytuned lower than a smaller diameter drum. Often drummers attempt to copythe pitches used by other drummers from recordings or from memory. Ingeneral, the desired tuning of a drum-set depends on the particularsound the drummer is looking for.

A drum produces a unique sound when its head is struck resulting fromthe resonance of the vibrating heads in conjunction with the shell ofthe drum. Striking a drum excites several rapidly-decaying, non-harmonicmodes of vibration resulting in a short, complex burst of sound. Drumtuning, by adjustment of a drum-head tension, to control pitch, tone andtimber is essential in establishing a pleasing drum sound. Tuning anymusical instrument involves playing a note, measuring or comparing thepitch of the note to some reference and adjusting the instrument's pitchuntil it conforms to the reference. However, assessing the pitch of adrum is complicated by the short duration and multiple non-harmonicresonances comprising its sound. Melodic instruments, on the other hand,produce continuous, periodic (harmonic) sounds with easy to measurepitch and are therefore much simpler to tune than a drum.

Drum tuning is typically done by ear, which is an art subject to theskill and taste of an individual musician. In addition, tuning by ear isinaccurate and has poor repeatability of results. Moreover, it isincreasingly difficult to tune by ear when tuning a drum-set where eachdrum typically is tuned to a different pitch or to tune the drum-set toa variety of popular drum-set sounds varying based on style of music orthe acoustic properties of the physical environment within which thedrum-set will be used.

Existing tuners for melodic instruments such as guitars and pianos areunsuitable for drum or drum-set tuning. They require a sustained toneduration that is longer than the duration of a drum sound and onlyoperate correctly on a periodic signal consisting of a singlefundamental and associated harmonics, not on the transient soundproduced by a drum. Drums typically create overtones unlike harmonicsthat are more easily distinguished from the fundamental frequency.Overtones are typically related to the fundamental frequency by aproduct of it π (pi), being related to the area and circumference of thedrum-head.

Mechanical tuning devices exist that measure the tension of thedrum-head by measuring the deflection of the head for a given force butdo not measure the pitch produced by a drum and thus suffer from avariety of inaccuracies due to drum skin thickness and temperaturevariations for example.

BRIEF SUMMARY

In one aspect, the invention features a method for resonance tuningcomprising receiving an analog signal in response to a resonance of astructure. The analog signal is digitized to create a plurality of timesamples. A burst of the time samples is detected, enabling a triggerthereby. A series of time samples is buffered from the plurality of timesamples in response to the trigger being enabled. A power spectrum isestimated by computing a Time-To-Frequency-Transform of the series oftime samples to create a series of frequency samples and squaring amagnitude of each of the frequency samples. One or more subsets offrequency samples from the series of frequency samples is selected. Eachsubset is associated with one or more spectral peaks and each spectralpeak includes at least one of the frequency samples having a firstmagnitude exceeding a first threshold and being spectrally adjacent toany other of the frequency samples in any other spectral peak within thesame subset by less than a second threshold. A fundamental spectral peakin a fundamental subset is determined. The fundamental subset includesthe spectral peak having the frequency sample at the lowest frequencygreater than zero. The fundamental spectral peak has the frequencysample with the largest first magnitude within the fundamental subset.

In another aspect, the invention features a resonance tuner comprising areceiver configured to generate an analog signal in response to aresonance of a structure. An analog to digital converter is incommunication with the receiver and is configured to generate aplurality of time samples of the analog signal. A pitch estimator is incommunication with the analog to digital converter and is configured tocalculate a fundamental spectral peak of the resonance of the structurefrom the plurality of time samples. A display module is in communicationwith the pitch estimator and is configured to display information to auser based on a fundamental spectral peak of the structure.

In another aspect, the invention features a drum-set tuner comprising areceiver configured to generate an analog signal in response to aresonance of a membrane of a drum. The analog to digital converter is incommunication with the receiver and is configured to generate aplurality of time samples of the analog signal. A pitch estimator is incommunication with the analog to digital converter and is configured tocalculate a fundamental spectral peak of the resonance of the membraneof the drum from the plurality of time samples. A user interface moduleis in communication with the pitch estimator. The user interface moduleincludes a one or more input controls configured to accept user inputsand a display configured to display information to a user based on afundamental spectral peak of the membrane of the drum. A pitch-setprocessor is in communication with the pitch estimator and the userinterface module. The pitch-set processor specifies the pitches of thevarious drum-heads in a set of drums.

In another aspect, the invention features a method for automatic drumtuning comprising measuring a plurality of pitches. Each measurement ismade after striking the drum-head proximal to a respective tuning lug ina plurality of tuning lugs of a drum-head. The lowest pitch lugassociated with the lowest pitch of the plurality of pitches isdetermined. A location of the lowest pitch lug and a deviation of thepitch of the lowest pitch lug from a selected pitch is displayed on auser interface.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The above and further advantages of this invention may be betterunderstood by referring to the following description in conjunction withthe accompanying drawings, in which like numerals indicate likestructural elements and features in various figures. The drawings arenot necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention.

FIG. 1 is a perspective view of a drum usable with an embodiment of theinvention.

FIG. 2 is graphical view of a measured time-domain response of oneembodiment of a drum when struck.

FIG. 3 is a graphical view of a calculated power-spectrum of thetime-domain response as illustrated in FIG. 2 and according to anembodiment of the invention.

FIG. 4 is schematic view of an embodiment of a Drum-Tuner according tothe invention.

FIG. 5 is a schematic view of an embodiment of the Pitch Estimator shownin FIG. 4.

FIG. 6 is a schematic view of an embodiment of the Power-SpectralEstimator shown in FIG. 5.

FIG. 7 is a schematic view of an embodiment of the Burst Detector shownin FIG. 5.

FIG. 8 is a schematic view of an embodiment of a Drum-Set Tuneraccording to the invention.

FIG. 9 is a schematic view of an embodiment of a Pitch-Set Processorshown in FIG. 8.

FIG. 10 is a top view of the drum shown in FIG. 1.

DETAILED DESCRIPTION

Embodiments of resonance tuners described herein provide for themeasurement of a fundamental frequency of a structure from a shortduration transient signal that typically includes other frequencies. Inone embodiment, the resonant structure is a vibrating blade in a turbineengine. The signal is measured by acoustic emissions from the blade. Inanother embodiment, the signal from the blade is measured with aninterferometer. In another embodiment, the resonant structure is a vocalcord from a person practicing musical scales. A microphone measures thesignal from the vocalist.

In a preferred embodiment, the resonant structure is a drum-head, with asignal measured by a receiver or sensor. The fundamental pitch of a drumis measured to facilitate drum tuning. A receiver produces an electricalsignal corresponding to the sound or vibration produced by the drum,after the drum is struck.

FIG. 1 shows a perspective view of a typical “tom-tom” drum 10 a, whichin one example, is used with the invention. The drum 10 a includes acircular membrane (drum-head) 12 suspended under tension on top of thedrum shell 14 by a hoop 16. The tension of the membrane 12 is adjustedby tightening the hoop 16 with a plurality of lugs 20 b, 21 b, 22 b 23 band 27 b (not shown in FIG. 1) and lugs 23 b, 24 b, 25 b and 26 b. Eachlug is affixed to the drum shell 14 by an attachment 18. The drum shownin FIG. 1 shows a single membrane 12, although in other embodiments asecond membrane is present on the opposing side of the drum. In oneembodiment, when an opposing membrane is present, the opposing membraneis “damped” or put on a towel or cushion to substantially prevent theopposing membrane from interacting with the membrane 12 during thetuning of membrane 12. Subsequent to tuning the membrane 12, theopposing membrane is tuned with membrane 12 damped. In anotherembodiment, the membrane 12 is tuned without damping the opposingmembrane.

Adjusting the tension of the membrane 12 requires adjusting each of thelugs to “clear” the drum and adjusting all of the lugs to achieve adesired pitch. Each lug is adjusted by imparting energy to the membrane12 in the vicinity of the lug. For example, to adjust lug 24 b, amusician would tap the membrane 12 near location 24 a. Similarly, toadjust lug 25 b, the musician would tap the membrane 12 near location 25a. Tapping is typically performed by striking the membrane 12 with adrum stick, although approaches where an impulse of energy is deliveredto the membrane 12 are envisioned.

FIG. 2 shows a measured time-domain response of an example embodimentwhen the membrane 12 is struck, at location 24 a for example. FIG. 3shows a calculated power-spectrum of FIG. 2 according to an embodimentof the invention. Multiple spectral peaks 36, 38, 40 and 42 arecalculated from the time-domain response shown in FIG. 1. The spectralpeaks are further grouped into subsets 32 and 34 based on their spectralproximity. For example, spectral peaks 36 and 38 are grouped into thesame subset 32 because they are sufficiently related based on frequencyseparation. Similarly, spectral peaks 40 and 42 are grouped into subset34. In the example shown in FIG. 2, spectral peaks 36 and 38 eachcorrespond to a fundamental frequency of one of two lugs, which are outof tune with respect to each other. In one example, spectral peak 36corresponds a fundamental frequency associated with lug 24 b, andspectral peak 38 corresponds to a fundamental frequency associated withnearby lug 25 b. The subset 32 is a “fundamental subset” because itcontains a spectral peak with the lowest frequency, excluding zero Hz.(D.C.). The spectral peaks 40 and 42 correspond to “overtones,” whichare undesirable higher frequency byproducts of the fundamental spectralpeak produced when the initial impulse travels across the circular drumand around the periphery of the drum, in addition to other complexpropagation paths. The highest amplitude spectral peak 36 within thefundamental subset 32 is chosen as the “fundamental spectral peak”associated with the lug 24 b being tuned. Subsequently, lug 24 b istuned so that the fundamental spectral peak 36 matches a selected pitch.Each lug of the drum 10 a is tuned in the manner described above untilall lugs are “cleared” and tapping the drum 10 a at any location 20 a,21 a, 22 a, 23 a, 24 a, 25 a, 26 a or 27 a produces substantially thesame fundamental pitch, which also corresponds to the selected pitch.

FIG. 4 shows an example embodiment of a Drum Tuner 50 a according to theinvention. In one example, the Drum Tuner 50 a is positioned over thedrum 10 a close enough (e.g. several inches) to detect the resonance ofthe membrane 12. The Drum Tuner need not be positioned near the lugbeing tuned. In one embodiment, the Drum Tuner is attached to the hoop16 and remains stationary throughout the entire tuning process of onedrum-head.

A receiver 52 detects a signal corresponding to a sound or vibrationfrom a resonant structure, the drum 10 a in FIG. 1 for example. In oneembodiment, the receiver includes a sensor 54, a microphone for example,and a preliminary amplifier (Preamp) 56. The Preamp 56 includes a lowpass filter to limit aliasing of subsequently sampled data. The signalreceived by the sensor 54 is amplified by the Preamp 56 and converted toa representative digital signal by an analog to digital convertor (ADC)58. In one non-limiting embodiment the ADC 58 includes a 12 bitsuccessive approximation register (SAR) operating at 8 k samples/secwith 8× decimation. The ADC 58 has a clock 60 with sufficient accuracyto determine the fundamental spectral peak 36. In one embodiment, theclock 60 is a crystal oscillator. For example, a clock 60 with 0.01 Hzaccuracy for a sample rate of 1 k samples/sec is sufficient. The digitalsignal from the ADC 58 is processed by a Pitch Estimator 62 thatestimates the fundamental spectral peak 36 from the signal received bythe receiver 52. In one embodiment, each of the functions performed bythe Pitch Estimator 62 are implemented with circuits. In anotherembodiment, each of the functions performed by the Pitch Estimator 62are performed with one or more processors. In yet another embodiment,the Pitch Estimator 62 uses a combination of circuits and processors toperform its function. The frequency estimate is provided to a UserInterface 64 that in turn displays at least one of the fundamentalspectral peak 36, a nearest musical note and the deviation of thefundamental spectral peak 36 from the selected pitch. The user providesa variety of inputs to the Drum Tuner 50 a with controls 68 on the UserInterface 64. For example, inputs provided by the user include theselected pitch, type of drum and what type of information should bedisplayed. In addition, the User Interface provides controls for storingand recalling specified and measured pitches. Other user inputs are alsoenvisioned within the scope of adjusting parameters of a resonant systemin response to detection of a fundamental frequency.

FIG. 5 shows an embodiment of the Pitch Estimator 62 as referenced inFIG. 4. The Pitch Estimator 62 stores a series of time samples from theADC 58 in a buffer 70. In one embodiment the Buffer stores 1024 timesamples. The number of samples stored in the Buffer is chosen to achievea sufficient sample size for accurate measurement, to store sufficientsamples for the duration of a drum burst, (e.g. 1 second) and to reducethe time required between successive measurements based on typical userexpectations. A Burst Detector 72 detects the start of a signal bursttypically corresponding to the beginning of the resonance of a structureafter the structure has received an impulse of energy, a drum strike forexample. In a preferred embodiment, the burst detection occurs after thecumulative energy of the digitized signal exceeds a pre-determinedthreshold. In another embodiment, the burst detector 72 determines whenthe digitized signal exceeds a threshold by a hysteresis value. Inanother embodiment, the burst detector 72 determines when a sum of aplurality of absolute values of the digitized signal exceeds athreshold, (or also a threshold value with hysteresis).

When a burst is detected by the Burst Detector 72, a Trigger signal 74is enabled. The enabling of the Trigger signal 74 initiates severaloperations. A pre-determined number of samples of digitized data fromthe ADC 58 are stored in the Buffer 70 for subsequent processing. In oneembodiment, the Power-Spectral Estimator 78 computes the power spectrumof the buffered data by transforming the samples into the frequencydomain and computing the magnitude-squared value of the samples. Aftertransformation from the time domain to the frequency domain, the dataare generally complex and computing the magnitude-squared value of eachsample consists of summing the squares of the real and imaginary values.

The Peak Selector 80 then identifies the spectral peaks of the powerspectrum. In a preferred embodiment, the spectral peaks are calculatedby first storing the magnitude-squared frequency domain samples in a“power array.” The power array is searched to identify the “maximumvalue power sample.” A “minimum peak power threshold” is then defined asa constant value below the maximum value power sample, typically 18 dBlower than the value of the maximum value power sample. The power arrayis then searched starting at the lowest frequency location and stoppingat the highest frequency location and storing the magnitude andfrequency of all the spectral peaks that are greater than the minimumpeak power threshold in a “peak array.” The spectral peaks are definedas samples from the power array with a zero value first derivative and anegative value second derivative when the power array is differentiatedwith respect to frequency. Typically, only the 10 lowest frequencyspectral peaks identified in the ascending search are stored in the“peak array.” The peak array will thus contain the first 10 spectralpeaks in ascending order of frequency all of which will exceed theminimum power threshold.

In a preferred embodiment, the opposing membrane to the membrane 12 inFIG. 1 is damped. The Frequency Estimator 82 searches through the peakarray and where any two successive spectral peaks are spectrallyadjacent within a limited frequency bandwidth (or threshold) of 10 Hzfor example, if the second spectral peak has a larger magnitude than thefirst spectral peak, the sequential position of the second spectral peakwill be swapped with the first spectral peak. After these steps, thefirst entry in the peak array corresponds to the estimate of thefrequency and magnitude (or power) of the fundamental spectral peak (orfundamental component) of the measure signal. This sorting of thespectral peaks results in a number of subsets, each with at least onespectral peak, where every spectral peak in a subset is spectrallyadjacent to another spectral peak within a limited bandwidth (orthreshold; e.g. 10 Hz). The spectral peak ordering method determines thefundamental subset having the spectral peak with the lowest frequencyand selects the spectral peak with the largest magnitude in thefundamental subset as the fundamental spectral peak.

In another preferred embodiment, the opposing membrane to the membrane12 in FIG. 1 is not damped (also referred to as “open”) and is allowedto couple resonant energy to the membrane 12 when the drum is struck.This coupling of resonant energy introduces a lower frequency spectralpeak below the frequency of the fundamental spectral peak generated whentuning with the opposing membrane damped. An open drum is tuned byaltering the tuning method used to tune a drum with the opposingmembrane damped to exclude the lowest frequency subset and choosing thefundamental spectral peak in the next highest frequency subset.

FIG. 6 shows an embodiment of the Power-Spectral Estimator 78 asreferenced in FIG. 5. The Power-Spectral Estimator 78 receives a seriesof buffered time samples from the Buffer 70 in FIG. 5 and optionallyconditions the samples with Zero-padding 84 and Windowing 86 prior toconverting the time samples to the frequency domain with a Fast FourierTransform (FFT) 88. Zero-padding 84 refers to adding zero-value samplesto the predominately non-zero value series of time samples to increasethe size of the FFT and hence the resulting frequency resolution. For anFFT with N samples, (an “N point FFT”), with sample rate Fs, thefrequency resolution is given by the equation ΔFs=Fs/N, so with a largersample size N, finer frequency resolution is obtained. For example, inone embodiment, the Buffer 70 stores 1024 samples. By appending 3072zero-value samples a 4096-point FFT is performed thereby increasingfrequency resolution by a factor of 4. Although the buffer couldoptionally store 4096 samples and zero-padding could be avoided, at aneffective 1 khz ADC sampling rate (or 8 kHz with 8 times decimation) theuser would have to wait four seconds to fill the buffer while thetypical drum burst only last one second as shown in FIG. 2.

The FFT is a specific implementation of a Time-To-Frequency-Transform,defined herein to refer to the conversion of time samples to thefrequency domain irrespective of the algorithm used. For example, inother embodiments the Time-To-Frequency-Transform uses either a DiscreteFourier Transform (DFT), a Discrete Cosine Transform (DCT), a FastCosine Transform, a Discrete Sine Transform (DST) or a Fast SineTransform (FST).

In a preferred embodiment Zero-padding 84 is used with Windowing 86.Because the series of time samples, with or without the Zero-padding 84,only represents a finite observation window, the resulting spectralinformation will be distorted after performing an FFT due to the ringingor sin(f)/f spectral peaks of the rectangular window. This is alsoreferred to as “spectral leakage.” To correct for this, each sample in aseries of time samples is multiplied by a sample from a fixed waveformsuch as a Hanning, Bartlett or Kaiser window. In this embodiment thesewindow functions have the same number of samples as the FFT (e.g. 4096),have symmetry about N/2 and increase in value from close to zero at thebeginning and end of the time series to a maximum value at the center ofthe time series. In a preferred embodiment, a Blackman-Harris windowfunction is used.

In a preferred embodiment the time samples are preconditioned withZero-padding 84 and Windowing 86 and are subsequently converting to thefrequency domain with an FFT processor. It is envisioned that anyDiscrete Fourier Transform (DFT) can be used to perform the frequencyconversion without being limited to using an FFT. Following the FFT 88,the series of frequency samples forming an estimate of the frequencyspectrum is converted into a power-spectral estimate by squaring each ofthe frequency samples with a Magnitude Squared function 90.

The Drum Tuner 50 a operates on either isolated drum strikes or on aseries of repetitive drum strikes. For repetitive drum strikes, theBurst Detector 72 re-triggers prior to the requisite number of timesamples (e.g. less than 1024 samples in one embodiment) and the shorterseries of time samples is zero-padded to the same length as an isolatedburst. For example, an isolated burst has 1024 samples and iszero-padded to 4096 samples by adding an additional 3072 zero valuesamples. A repetitive strike occurring every 500 ms only has 512 samplesin one example and would be extended to 4096 samples by adding 3584 zerovalue samples. In one embodiment, the Zero-Padding 84 detects the numberof samples stored in the Buffer 70 and adjusts the number of zero valuesamples to be added accordingly, such that 4096 time samples result.

Spectral averaging is performed with an Averager 100 on the estimatedpower spectrum output for each successive burst thereby increasing theprecision of the Power-Spectral Estimator 78 and the resulting estimateof the fundamental spectral peak. Spectral averaging is performed bytaking the average of the magnitude-squared value of each frequencysample of the series of frequency samples with the magnitude-squaredvalue of a corresponding previously stored frequency sample. Forexample, the 2nd frequency sample of a new burst is averaged with thesecond frequency sample of a previous burst. Zero padding occurs at theend of a shortened burst of time samples, so the proper alignment oftime samples from current and previous bursts is maintained.

In one embodiment, the Burst Detector 72 of FIG. 5 includes a comparatorthat compares the digitized data from the ADC 58, or it's absolutevalue, to a threshold to enable the burst-detected Trigger 74. In apreferred embodiment shown in FIG. 7, energy detection is used. Energydetection is more complex but offers more reliable burst detection inthe presence of noise sources and glitches. The energy of severalconsecutive samples (e.g. 8 samples in one embodiment) is calculated bysquaring and summing the samples together. Specifically, a plurality ofsample and hold circuits 102 a, 102 b through 102 n (generally 102) holdthe time samples from the ADC 58. In the example where the ADC 58 uses12 bit resolution, each sample and hold circuit 102 is a 12 bit registerin one embodiment. In another embodiment, the sample and hold circuit102 is a First In First Out (FIFO) memory. Each time delayed sample fromeach sample and hold circuit 102 including a time sample without a delayis squared with circuits 104 a, 104 b, 104 c through 104 n (generally104). Specifically, a sample with no delay is squared with circuit 104a, a previous sample held by sample and hold 102 a is squared withcircuit 104 b, and so on. Each squared sample is summed with a summingcircuit 106, compared to a Threshold 110 with a subtraction circuit 108,and activates a Trigger 74 if the value is positive as determined by acomparator 112. In a preferred embodiment, the value of the Threshold110 is 5% of the peak burst energy. In an alternative embodiment usingvoltage level detection the threshold is 20% of the peak voltage.

FIG. 8 shows a Drum-Set Tuner 50 b as an alternative embodiment to theDrum Tuner of FIG. 4 including an additional Pitch-Set Processor 120 tofacilitate tuning of multiple drums. The Pitch-Set Processor 120 selectsthe pitches (e.g. the desired fundamental spectral peak) of eachdrum-head in the drum-set based on criteria provided by the user via aUser Interface 64. For example, the user will specify the sizes andnumber of drums in the drum-set and the type of tuning desired, such asa chord, interval, type of sound, or a famous drummer's tuning. ThePitch-Set Processor 120 then indicates the selected pitch for eachdrum-head in the drum set thereby assisting the user in tuning each headof each drum to the correct pitch. In addition, the user can storespecific or measured drum-set tunings in the Pitch-Set Processor 120 tobe recalled at a later time. This storage mode includes pitches ormusical notes entered by the user with controls 68 and communicated tothe Pitch-Set Processor at 124 or pitches measured with the Drum Tunerby the user and communicated to the Pitch-Set Processor at 122. TheSelected Pitch calculated by the Pitch-Set Processor 120 is communicatedto the Display 66 at 126.

FIG. 9 shows a preferred embodiment of the Pitch-Set Processor 120 thatdetermines the Selected Pitch 126 b for tuning each of the drums in aset of drums to pitches comprising the notes in an extended Major chord.For example, the Major chord has pitches that are in increasing orderrelative to the lowest or Base Pitch 124 a are 1, 5/4, 3/2, 2, 5/2 and3, shown collectively as Pitch Multiples 136. The Base Pitch 124 a andthe Selected Drum 124 b from the drum-set are supplied from the UserInterface 64. The Selected Pitch 126 b is computed according to itsposition in the chord as a product 132 of the Base-Pitch 124 a and theselected Pitch Multiple 134, the Pitch Multiple 136 being selected byMultiplexor 134 controlled by the Selected Drum 124 b. In addition tocomputing the Selected Pitch 126 b, the Deviation 126 a of the SelectedPitch 126 b from the Pitch Estimate 122, (e.g. the fundamental spectralpeak) is calculated by subtracting the Selected Pitch 126 b from thePitch Estimate 122 with the subtraction circuit 130. The Selected Pitch126 b and the Deviation 126 a are both conveyed to the Display 66 at 126shown in FIG. 8.

FIG. 10 is top view of the drum 10 a shown in FIG. 1 illustrating anautomatic tuning method according to a preferred embodiment of theinvention. The Drum Tuner of FIG. 4 enables a user to tune a drum bymeasuring the individual pitches (e.g. the fundamental spectral peak)near each tuning lug and making corresponding adjustments to the lugtensions until the pitches are uniform. However, this is an iterativeapproach involving repeated pitch measurements and lug adjustmentsbecause the tension and pitch of the drum-head adjacent to a tuning lugdepends not only on the tension of the closest lug but also to a lesserextent on the tension of all the other lugs. Consequently, there is aninteraction between the tensioning of each lug.

For example, tightening a lug to raise the nearby drum-head pitch willalso raise the pitch near the two adjacent lugs and the opposite lug tosome extent. This inherent interaction between the tension of a singlelug and the pitch of other lugs complicates drum-head tuning andincreases the number of iterations that are required before uniformityis achieved. It would therefore be advantageous to automate thedrum-head tuning process to account for the tension lug interaction andthereby minimize the number of iterations to simplify and speed up thetuning of a drum-head. This would also save the user the task ofremembering the various pitches around the drum-head.

In the process of tuning a drum-head, it is possible to either increasethe tension of the lugs corresponding to lowest pitch, or to lower thetension of the lugs corresponding to highest pitch, the former beingpreferable. Lowering the tension of a lug results in a partialde-seating of the lug screw and a less predictable or stable tensionsetting. As such, the following description is based on increasingtuning lug tension to raise the pitch of the lower pitched sections ofthe drum-head to match the pitch of the higher pitched sections.

Referring to FIG. 10, an embodiment of a drum 10 a has 8 lugs 20 b, 21b, 22 b, 23 b, 24 b, 25 b, 26 b and 27 b (generally “lugs”). Each lughas a corresponding location 20 a, 21 a, 22 a, 23 a, 24 a, 25 a, 26 aand 27 a (generally “tap location”) where the drum-head is struck duringtuning. The automatic tuning process begins by tuning each of the lugsas previously described and saving the pitch estimate proximal to eachlug. A plurality of pitch-pairs is then calculated by averaging thepitch proximal to each lug with the pitch proximal to a diametricallyopposed lug. For example, the pitch 20 a proximal to lug 20 b isaveraged with the pitch 24 a proximal to 24 b, and similarly for lug 21b with 25 b, 22 b with 26 b, and 23 b with 27 b resulting in fourpitch-pairs. For each of the four resulting pitch-pairs, the pitch-pairwith the lowest average pitch is chosen as a “primary pitch-pair.”

For example, in the embodiment shown in FIG. 10 the average pitchassociated with lugs 20 b and 24 b has the lowest average pitch and theprimary pitch-pair is as shown based on pitch measurements at 20 a and24 a. The primary pitch-pair has a first lug, 20 b and a second lug 24b. Adjusting the pitch associated with the first lug 20 b will affectthe pitch associated with all lugs, however the greatest effect will bewith respect to the adjacent lugs 27 b and 21 b due to the forces fromthe hoop 16, and also with respect to the diametrically opposed lug 24b.

After establishing which of the four pitch-pairs is the primarypitch-pair, if either the first lug 20 b or the second lug 24 b havesubstantially different pitches associated with them (e.g. a 0.25 Hzdifference) then the lower pitch of the two lugs will be adjusted first,then the other lug will be adjusted. Subsequently, the next lowestpitch-pair will be chosen as the primary pitch-pair and a similaradjustment made until all pitches associated with each lug are adjusted.

If the pitch associated with the first lug 20 b and the second lug 24 bof the primary pitch-pair are not substantially different then thedetermination of which of the first lug 20 b and the second lug 24 b isto be adjusted next then depends on the secondary effects on theadjacent lugs. A first adjacent pitch-pair is determined by averagingthe pitch associated with the lugs 27 b and 21 b adjacent to the firstlug 20 b. A second adjacent pitch-pair is determined by averaging thepitch associated with the lugs 25 b and 23 b adjacent to the second lug24 b. If the first adjacent pitch-pair has a lower average pitch thanthe second adjacent pitch-pair then the first lug 20 b is adjustedbefore the second lug 24 b, otherwise the second lug 24 b is adjustedfirst. Subsequently, the next lowest pitch-pair will be chosen as theprimary pitch-pair and a similar adjustment made until all pitchesassociated with each lug are adjusted. In the example embodiment of adrum 10 b, eight lugs are shown. It should be appreciated that theautomatic tuning method similarly applies to other drum embodiments.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method, or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wire-line, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

While the invention has been shown and described with reference tospecific preferred embodiments, it should be understood by those skilledin the art that various changes in form and detail may be made thereinwithout departing from the spirit and scope of the invention as definedby the following claims.

What is claimed is:
 1. A tuning apparatus, comprising: a processor thatreceives a desired fundamental frequency or note and determines anovertone frequency or note of at least one drumhead of a drum inresponse to the received desired fundamental frequency or note, theovertone frequency or note of the at least one drumhead being determinedsuch that the overtone frequency or note is proportional to the receiveddesired fundamental frequency or note; and an output at the processorthat outputs a value corresponding to the determined overtone frequencyor note of the at least one drumhead.
 2. The tuning apparatus of claim1, wherein the at least one drumhead includes a first membrane at oneside of the drum and a second membrane at an opposite side of the drumas the first membrane.
 3. The tuning apparatus of claim 1, furthercomprising: a receiver configured to generate a signal in response to aresonance of the drum; a frequency measuring device in communicationwith the receiver, and configured to measure a frequency of the drumfrom the signal; and an interface module in communication with thefrequency measuring device, and configured to display information to auser based on a frequency of the drum.
 4. The tuning apparatus of claim1, wherein the determined overtone frequency or note of the at least onedrumhead includes frequencies or notes of lowest overtones of the topand bottom drumheads, respectively.
 5. The tuning apparatus of claim 1,wherein the desired fundamental frequency or note is received by theprocessor from a user interface.
 6. The tuning apparatus of claim 1,wherein the desired fundamental frequency or note is determined from apitch-set processor.
 7. A drum tuning system comprising: a tuningprocessor that receives a desired fundamental frequency or note anddetermines an overtone frequency or note of each of a top drumhead and abottom drumhead of a drum in response to the received desiredfundamental frequency or note; an input that presents the desiredfundamental frequency or note to the tuning processor; a frequencymeasuring device that measures a frequency of the drum in response to anexcitation of the drum; and an output that outputs at least one of adetermined overtone frequency or note and a measured frequency inresponse to the excitation of the drum.
 8. The drum tuning system ofclaim 7, wherein the input includes a user interface.
 9. The drum tuningsystem of claim 7, wherein the input includes a pitch-set Processor. 10.The drum tuning system of claim 7, wherein the determined overtonefrequency of each of the top and bottom drumheads includes a lowestovertone frequency.
 11. The drum tuning system of claim 7, wherein theoutput outputs an actual fundamental frequency that is at or close tothe desired fundamental frequency according to the determined overtonefrequency of the drumheads in response to a drum tuning adjustment. 12.The drum tuning system of claim 11, wherein the drum tuning adjustmentincludes tuning the top and bottom drumheads to one or more lowestovertone frequencies determined by the tuning processor.